The present invention relates generally to refrigeration systems, and more particularly, to an expander compressor unit which utilizes the work expended in direct expansion of a refrigerant to power a turbine which drives a small compressor to aid the primary compressor of a refrigeration system in compressing gaseous vapors from evaporator pressure to condenser pressure.
Vapor compression refrigeration cycles and apparatus for carrying out these cycles are well known. In theoretical vapor compression refrigeration, saturated vapor refrigerants at low pressure enter a compressor and undergo isentropic compression. The high pressure vapor enters a condenser and heat is rejected from the fluid at constant pressure from the condenser. The working fluid leaves the condenser as a saturated liquid. An isenthalpic throttling process follows across an expansion valve or capillary tube. The working fluid is then evaporated at constant pressure with the working fluid absorbing heat to complete the cycle.
In the past, the design of direct expansion refrigeration units has not generally taken advantage of the energy or available work lost in the execution of the cycle through the throttling or free expansion of the liquid refrigerant into the evaporator of the refrigeration machine. Generally, only limited use has been made of the conversion into mechanical energy of the kinetic energy possessed by the refrigerant which flows from the high pressure side to the low pressure side of the refrigeration system. For example, it is known to power a compressor with the refrigerant discharged from the capillary tube. The compressor is arranged in the auxiliary circuit which includes a second evaporator. In this way, a two temperature system is provided in which the additional evaporator can be operated within a temperature range lower than that of the evaporator in the main circuit. Typical of systems of this type is the refrigeration system method shown in U.S. Pat. No. 2,519,010.
Other attempts at utilizing the kinetic energy of refrigerant expansion have concentrated mainly on pumping or recirculating refrigerant or lubricants. For example, U.S. Pat. No. 2,763,995 discloses the use of high pressure refrigerant directed against the blades of a turbine. The turbine has a shaft which is connected to a centrifugal pump. The pump serves to recirculate oil rich liquid refrigerant back to the compressor.
Generally, however, systems as described above which utilize or attempt to utilize the work expanded in the throttling or expansion process have not found wide acceptance. As pointed out, most of these systems attempt to utilize the kinetic energy to perform some auxiliary operation such as the circulation of lubricating fluid. Accordingly, the equipment necessary for its recovery has not been thought to be economically feasible. Very little work has been done in utilizing this energy to improve the performance and efficiency of the basic vapor compression refrigeration cycle.
The present invention provides an expander compressor in which the saturated liquid from the condenser is expanded and flashed through nozzles of a shaft mounted rotor causing a tangential propelling force to be applied to the rotor and an attached turbine shaft. The turbine shaft drives an axial compressor unit. On the compressor side, saturated vapor from the evaporator enters the vane chamber of the compressor and is compressed into the super heat region and is discharged into an annular chamber either to the primary compressor or directly to the condenser of the air conditioning unit. A small fraction of the saturated liquid refrigerant entering the unit is utilized to provide full film lubrication of the shaft bearings. The compressor section of the unit may include an appropriate inducer section to pull the refrigerant into the blades of the compressor section. The rotor can be modified for various capacity systems by changing the nozzle size or by adding more discharge passages to the expander section.